Process of preparing metal for use in unidirectional current carrying devices



June 21, O GRONDAHL 1,863,843

PROCESS OF PREPARING METAL FOR USE IN UNDIRECTIONAL CURRENT CARRYINGDEVICES Original Filed Jan. 7, 1925 Patented June 21, 1932 UNITEDSTATES- PATENT OFFICE LABS O. GR ONDAHL, OF PITTSBURGH, PENNSYLVANIA,ASSIGNOR TO THE UNION SWITCH & SIGNAL COMPANY, 01' SWIBSVALE,PENNSYLVANIA, A CORPORATION 01 PENNSYLVANIA PROCESS OF PREPARIN G METALFOR USE IN UNIDIRECTIONAL CURRENT CARRYING DEVICES Original applicationfiled January 7, 1925, Serial No. 1,111. Patent No. 1,640,835. Dividedand thll application filed July 1, 1927, Serial No. 202,811. RenewedJanuary 15, 1982.

My invention relates to unidirectional current carrying devices, andparticularly to processes of preparing metal for use in such devices.

The present application is a division of my copending application,Serial No. 1,111, filed January 7, 1925, for unidirectional currentcarrying devices, now Patent No. 1,640,335, August 25, 1927.

I will describe one method of preparing metal for use in unidirectionalcurrent carrying devices, and will then point out the novel featuresthereof in claims.

In the accompanying drawing, Fig. 1 is a view showing in elevation oneform of blank ready to be prepared for use in a unidirectional currentcarrying device in accordance with my invention. Fig. 2 is a viewshowing in vertical section the blank shown in Fig. l as it appears atone point in a process embodying my invention. Fig. 3 is a view showingin vertical section a unit for use in a unidirectional current carryindevice after the completion of a process em bodying my invention.

Similar reference characters refer to similar parts in each of the threeviews.

Referring to the drawing, the reference character A designates a blankof suitable material, such as copper. As here shown,

blank is of circular configuration and is provided with a centralaperture A although this particular form is not essential. In thepractice of my invention this blank is first cleaned; an oxide is thenformed directly on the metal by oxidizing the-metal at a relatively hightemperature in an atmosphere containing oxygen. In the case of copper,the temperature should be in the neighborhood of 1000 degrees centigradeand below the melting point of copper, such a temperature apparentlybeing essential to the formation of a compound having the properhomogeneity, that is, non-porosity. In preparin this oxide there isalways formed a very thin layer of cupric oxide on the surface of thecuprous oxide which constitutes the main body of the oxide. The blanknow appears as shown in Fig. 2, in which A is the copper b1ank,"1 is thelayer of cuprous oxide,

and 2 is the coating of cupric oxide, the two oxlde coatings beinggreatly magnified in thickness in this view. The layer of cupric oxideis removed by suitable means, such, forexample, as emery cloth, as asand blast, or nitric acid. Furthermore, the layer of cuprous oxide 1 onone surface of the blank is preferably also removed, and the finishedunit then has the appearance shown in Fi 3.

In order to insure good results, the sur ace of the copper which is tocarry the cuprous oxide should be smooth and chemically clean.

. Some sheet copper has the appearance of having wrinkled on one sidewhile cooling; such sheets will produce a good rectifier when the smoothside is used to carry the oxide, and a pgor rectifier when the wrinkledside is so use I I have found that a unit prepared in accordance with myinvention will have the characteristic of ofiering a great deal hi herresistance to the electric current flowing rom the metallic copper A tothe oxide 1 than the current flowing in the other direction.

The finished unit shown in Fig. 3 may be utilized in the manner shownand described in my (parent application, Serial No. 1,111, referre tohereinbefore.

Although I have herein shown and described only one process of preparingmetal for use in unidirectional current carrying devices and embodyingmy invention, t is understood that various changes and modifications maybe made therein within the scope of the appended claims withoutdeparting from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. The process of preparing a unidirectional current carrying junctionwhich consists in forming a smooth chemically clean surface on a copperblank, heating the blank to form oxides on said surface, and removingthe cupric oxide.

2. The process of preparing a unidirectional current carrying junctionwhich consists in cleaning a copper blank, heating the blank to formcuprous oxide next to the copper and cupric oxide over said cuprousoxide, and removing the cupric oxide.

3. The process of preparing a unidirectional current carrying junctionwhich consists in heating a copper blank in the presence of oxygen toform oxides thereon, removing the oxides from a portion of the blank,andremoving only the outer high resistance coating from other parts ofthe blank.

4. The process of preparing a unidirectional current carrying junctionwhich consists in heating a copper blank to substantially 10 00centigrade in an oxidizing atmos phere.

5. The process of preparing a unidirectional-current carrying junctionwhich con- 15 sists in heating a copper blank to substantially 1000centigrade to form coatings of cuprous oxide and cupric oxide thereon,and removing the cupric oxide.

6. The method of obtaining a permanent :0 rectifying junction betweencopper and onprous oxide which permits substantially unobstructed flowof electrons only in the direction from the copper to the oxide, whichcomprises oxidizing a smooth surface of a :6 copper body at atemperature of about 7. The method of obtaining a permanent rectifyingjunction between copper and cuprous oxide which permits substantiallyun- 00 obstructed flow of electrons only in the direction from thecopper to the oxide which comprises heating said copper body in anatmosphere containing oxygen to a temperature above'800 C. but below themelting temperature of copper, forming thereby on said copper a layer ofcuprous oxide having an outer layer ofcupric oxide.

8. The method of obtaining a permanent rectifying junction betweencopper and cuprous oxide which permits substantially unobstructed flowof electrons only in the direction from the copper to the oxide, whichcomprises heating said copper body in an atmosphere containing oxygen toa temperature above 800 C. but below the melting temperature of copper,forming thereby on said copper a layer of cuprous oxide having an outerlayer of cupric oxide and removing the layer of cupric oxide.

9. The method of obtaining a permanent rectifying junction betweencopper and enprous oxide which permits substantially unobstructed flowof electrons only in the direction from the copper to the oxide, whichcomprises heating said copper body to a temperature between 1000 and1050 in an atmosphere containing oxygen, forming thereby on said coppera layer of cuprous oxide having an outer layer of cupric oxide.

In testimony whereof I aflix my signature.

LARS O. GRONDAHL.

